The new building being put up by Gold Coast real estate developer Mark Goodman & Associates at 310 North Sangamon Street is going to be the largest “passive house” office building in the nation.

“Passive house” is a design strategy that tries to reduce the amount of energy a building uses as much as possible. Ideally, a fully passive house building would take zero energy from the grid. But the Passivhaus-Institut in Darmstadt, Germany lays out the rules for this sort of thing, and is OK with buildings that get pretty close. Still, according to Wikimopedia, the building still must:

Be designed to have an annual heating and cooling demand of not more than 4,755 BTU/square foot OR be designed with a peak heat load of 1.2 hp/1000 square foot.

Total primary energy consumption must not be more than 19,020 BTU/square foot.

The building must not leak more air than 0.6 times the building’s volume per hour at 0.0073 psi.

All those numbers are enough to make you break out the old HP-35. But they’re not unexpected, because… Germans.

It wasn’t a fully functioning house, but was way nicer and slightly bigger than the “luxury” studio apartments we’ve rented in Chicago, even though it was made out of used shipping containers.

Now imagine Das Haus all grown up as Das Bürogebäude, and you get an idea what’s going on at 310 North Sangamon, where fellow Gold Coasters SCB are doing the design.

That building will be 12 stories tall, with 268,000 square feet of office space and 7,800 square feet of retail space. Yet it will use 86% less energy on heating and 46% less energy on cooling than a similarly sized building.

According to the Passive House Institute of the U.S., there were 1,200 passive house buildings in the country last year; mostly passive house houses. Now Chicago will make it 1,201.

On average, a passive house building costs 5% — 10% more than a regular building, some of which can be recouped through lower utility bills. But can you really put a price on hugging Mother Earth? Or all the free publicity you get from doing the Right Thing™?